“No other toxin the world has as long a list of diseases associated with it,” said Hamilton, whose lab at MBL first discovered that arsenic is a potent endocrine disruptor and a powerful suppressor of innate immunity.

Arsenic, a naturally occurring chemical and the 20th most abundant element in the universe, is odorless, colorless and tasteless in water. It has been used as a drug for more than 2,500 years, Hamilton said.

“Rasputin used to eat arsenic because he felt it would make him stronger and protect him if he ever got poisoned,” he said. The white powder was used to color items like drapes and clothing, and women even used it in cosmetics as a whitening agent. But today, we know that arsenic--just like any substance, if the dose is high enough--can be poisonous.

Hamilton said today, more than 25 million Americans are drinking excess arsenic from private wells—which are not regulated by cities, states or the federal government. He said chronic human exposure to inorganic arsenic at sub-acute doses has been linked to increased risk of cancers (especially lung, skin and bladder), Type 2 diabetes, vascular and cardiovascular disease, and reproductive, developmental and neurological problems.

New Hampshire has one of the worst arsenic problems, and Hamilton said studies there have shown a connection between drinking excess arsenic and a two-to-three-fold increase of skin and bladder cancers.

“It’s the biggest water contamination problem,” Hamilton said. “It dwarfs the effect of all other water chemical combined—in New Hampshire and I’d say nationally.”

Other states with public water supplies that come from ground water and have arsenic problems include areas in New Mexico, Arizona, Texas, Colorado and California, but those supplies are regulated by the EPA (the EPA has set the arsenic standard for drinking water at 10 parts per billion). “It’s the private wells where people just don’t know what they’re drinking,” Hamilton said. He said most water supplies in the U.S. come from surface water, in which there is virtually no arsenic.

In studies with mice, Hamilton said that mice on arsenic that are exposed to the H1N1 flu will never recover from the flu (because their immunity is suppressed), and that arsenic also decreases their success in mating.

One of the biggest arsenic studies over the last few decades has occurred in Chile, where a town switched to an arsenic-laden water supply, unbeknownst to them. “They drank this for 12 years and then in 1970 they figured it out and switched water supplies again,” Hamilton said. “So there was this 12-year-period where they were exposed to arsenic.” Studies have been conducted between this town and a neighboring town (with no arsenic). In the town with the excess arsenic, studies have shown a moderate increase in a variety of diseases and a significant increase in bronchiectasis, a chronic lung disease.

Other studies have occurred in Bangladesh, where tube wells were put into service as a way to manage the cholera problem (from surface water). The use of water from the wells led to a massive population exposure to excess arsenic in the drinking water. Hamilton also said much of the exposure to arsenic there comes from rice fields, which are irrigated with water from the same wells.

The good news, Hamilton said, is that arsenic doesn’t accumulate in our bodies. “If you’re exposed to it episodically, it’s not a big deal,” he said. “What it takes is drinking it every day.” He said it accumulates at high doses temporarily and can be found in a person’s hair and nails. He said in places like New Hampshire, it’s more of an outreach problem than a science problem. If the wells are found to have high levels of arsenic, the water can be filtered with a reverse osmosis systems. “The message,” he said, “is test your well.”